A leg length discrepancy (LLD) is a condition where one lower limb is noticeably shorter than the other, creating an imbalance that can affect a person’s biomechanics. This difference in length forces the body to compensate, which often manifests as an altered gait, or walking pattern, and poor posture. While the condition can be a source of discomfort or pain over time, it is highly treatable, and medical professionals can implement a variety of effective strategies to restore symmetry and function. The approach to correcting the discrepancy depends entirely on the underlying cause and the severity of the measured difference.
Structural Versus Functional Causes
The initial step in addressing an LLD involves determining whether the cause is structural or functional, as this distinction dictates the treatment pathway. A structural LLD represents a true anatomical difference in bone length. This type of discrepancy typically arises from congenital conditions, a growth plate injury during childhood, or imperfect healing following a severe fracture.
A functional LLD is more common and occurs when the legs are anatomically the same length, but one appears shorter due to issues originating outside the leg bones themselves. These issues often involve misalignments in the pelvic girdle, such as a pelvic tilt or rotation, or muscle contractures in the hip or back. Functional discrepancies can also stem from problems in the feet, such as excessive foot pronation, which effectively shortens the limb’s functional length.
How Leg Length Discrepancy Is Measured
A physician will begin with a clinical assessment. This can involve measuring the distance from a fixed point on the pelvis, such as the anterior superior iliac spine, down to the medial malleolus at the ankle. Another common clinical technique involves placing calibrated wooden blocks of known height under the shorter heel until the pelvis appears level.
While clinical methods offer a useful starting point, imaging techniques provide the precise measurement required for treatment planning. The most accurate method for quantifying structural LLD is a Scanogram or a computed tomography (CT) scanogram. This technique uses low-dose X-rays taken with a calibration ruler to measure the exact lengths of the femur and tibia on both sides. The precise measurement of the discrepancy determines if non-surgical or surgical intervention is appropriate, particularly if the difference is less than 2.5 centimeters or significantly greater.
Conservative Management Strategies
For most patients with a small to moderate structural discrepancy, typically under 2.5 centimeters, conservative management is the preferred intervention. The most straightforward non-invasive fix is the use of shoe lifts or heel lifts to equalize the length difference. These lifts can be placed inside the shoe as an insole for smaller discrepancies or added externally to the sole for greater height requirements.
Custom foot orthotics play a significant role, particularly in addressing functional LLDs originating from foot mechanics. An orthotic can be designed to correct excessive pronation or supination, which are common compensatory patterns that create the appearance of a discrepancy. By stabilizing the foot and ankle, the custom insert helps to rebalance the body’s weight distribution.
Physical therapy (PT) addresses functional LLDs caused by muscle and soft tissue imbalances. A tailored PT program focuses on stretching tight structures like the hip flexors or hamstrings and strengthening weak muscle groups, such as the core and gluteal muscles. This targeted approach works to normalize the pelvic position and spinal alignment, thereby eliminating the functional discrepancy. PT is also a standard component of recovery for structural LLD, ensuring better gait mechanics and overall musculoskeletal health.
Surgical Options for Correction
Surgical intervention is generally reserved for structural LLDs that exceed 2.5 centimeters, as these larger differences are difficult to manage with shoe lifts. For children and adolescents who are still growing, one option is a procedure called epiphysiodesis, which slows the growth of the longer leg. This involves surgically fusing or temporarily arresting the growth plate of the longer limb, allowing the shorter leg to catch up.
For adults and those with a finished growth cycle, limb shortening is an option where a segment of the bone in the longer leg is surgically removed. This procedure is typically performed on the femur or tibia, and the remaining bone segments are fixed together with plates and screws. Shortening is usually limited to a few centimeters to avoid excessive tightening of the surrounding muscles and nerves.
The most complex technique for correcting severe LLD, often greater than five centimeters, is limb lengthening through distraction osteogenesis. This involves a surgical procedure called a corticotomy, where the bone is carefully cut, leaving the surrounding soft tissues and blood supply intact. An external fixator or an internal lengthening nail is then applied. After a short latency period, the device is used to gradually pull the bone segments apart, typically at a rate of about one millimeter per day. This slow, controlled separation stimulates the body to generate new bone tissue in the gap, effectively lengthening the limb.